Image credit: HawaiianMama, Wikimedia Commons; image source; larger image
HyperPhysics: Global Positioning Satellites
The image shows a Global Positioning System (GPS) receiver that pinpoints a cyclist's location to an accuracy of about 10 m. The receiver analyzes radio signals from several GPS satellites, each containing an atomic clock accurate to about one second every 30,000 years. For more on GPS, see HyperPhysics: Global Positioning Satellites and also this NASA site.
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Do you have a GPS at home? Try taking it outside and exploring your area with Geocaching. It's a modern-day treasure hunting game, using your GPS to find packages left by fellow "Geocachers." All you have to do is sign up on the website, search for geocaches near you, put in the coordinates, and go! Be sure to have an adult with you.